A Manhattan man slapped his ex-girlfriend with a lawsuit claiming she absconded to California with their mixed-breed border collie.

John Lancaster, 45, claims he had a handshake agreement with former gal pal Samantha E. Addy, 34, for shared custody of Hoover, according to the Manhattan Supreme Court suit filed Friday.

Lancaster and Addy alternated possession of the pooch every two weeks and had agreed that if either one moved out of state the person who stayed in New York got to keep Hoover, the suit says.

But Lancaster went on a short trip this past August and returned to find both his ex and his pet had left town, he says. Addy called to say that she was permanently relocating to San Francisco — and she had taken Hoover.

Lancaster says the dog belongs to him because he purchased the pup for $816.56 in November 2009 and “has paid all costs and expenses associated with ownership,” he claims in the suit.

He is demanding the mutt’s return or $816.56.

Addy did not immediately return calls for comment.

Hoover’s case comes just a few weeks after a Manhattan divorce judge issued a landmark ruling granting a one-day hearing to a lesbian couple fighting over custody of their miniature dachshund Joey.